This invention relates to an improved grain dryer and, more particularly, to an improvement in a concurrent-countercurrent flow type grain dryer of the type disclosed in U.S. Pat. No. 3,727,323, U.S. Pat. No. 3,302,297, U.S. Pat. No. 3,710,449, or U.S. Pat. No. 3,913,242, each of which is incorporated herewith by reference.
The above patents disclose, in general, a grain dryer wherein wet grain is introduced at the top of a bin for flow in a generally downward direction. Dried grain is withdrawn from the bottom of the bin simultaneous with the feeding of wet grain at the top of the bin. Heated air is introduced through hot air inlet ducts adjacent the top of the bin for flow in a direction which is concurrent with the grain flow. Simultaneously cool air is introduced adjacent the bottom of the bin near the grain discharge outlets for flow in a direction countercurrent to the direction of grain flow. Exhaust ducts are positioned intermediate the hot air inlet ducts and cold air inlet ducts for discharge to the atmosphere. Thus, the hot air will be somewhat reduced in temperature and moisture laden, thereby removing moisture from the grain within the dryer. The cool air will be somewhat heated relative to its initial inlet temperature and may also include an additional moisture content.
By such apparatus, improved grain drying results are observed. It has been noted, however, that the moisture content of discharged air is not at all times a saturated moisture content. Consequently, some energy losses are observed with a drying system of the type described in the previously identified patents. Energy loss is especially accentuated or increased as air is moved through the bin at faster rates and at relatively higher pressures. To improve the efficiency of the grain dryer of the concurrrent-countercurrent type, the subject matter of the present invention was developed.